1. Field of the Invention
The present invention relates to a dehydration catalyst and a process for producing a monoalkylether of a dihydric phenolic compound using the same. More particularly, the present invention relates to a dehydration catalyst having an enhanced catalytic activity for gas phase dehydration reactions, for example, gas phase etherification and esterification reactions, and a satisfactory mechanical strength, and a process for producing a monoalkylether of a dihydric phenolic compound by dehydration-reacting a dihydric phenolic compound with a lower alkyl alcohol in the gas phase in the presence of the above-mentioned catalyst, with a high conversion at a high selectivity. The monoalkylether of the dihydric phenolic compound is useful as a starting material for the production of perfumes, scents, essences and medicines.
2. Description of the Related Art
Processes for producing a monoalkylether of a dihydric phenolic compound by a gas phase etherification reaction or a gas phase esterification reaction, particularly a gas phase dehydration reaction of a dihydric phenolic compound with a lower alkyl alcohol are known in (1) Chem. Abs., 55-7336 (1961) and Masloboino-Zhirovaya Prom., 26, 10, 24 (1960), wherein a catalyst comprising phosphoric acid and boron is used, (2) Japanese Examined Patent Publication No. 53-35,062, No. 55-33,658 and No. 53-6618, wherein a catalyst comprising aluminum, phosphorus, boron and oxygen is used, (3) Journal of The Chemical Society of Japan, 12, 2331 (1985) and Japanese Examined Patent Publication No. 56-25,213, wherein a kaolin catalyst is used, and (4) Japanese Unexamined No. 4-341,345 in which a catalyst comprising aluminum, phosphorus, titanium, silicon and oxygen is used.
The above-mentioned process (1) is disadvantageous in that the target product, for example, guaiacol, is produced at an unsatisfactory selectivity of about 80 to 90% and, due to an decrease in the content of a BPO.sub.4 component in the catalyst during the reaction, the catalyst activity life is very short.
The process (2) is disadvantageous in that the catalytic activity and mechanical strength of the catalyst gradually decrease.
The process (3) is unsatisfactory in that the target product is produced at an insufficient selectivity of about 80%.
The process (4) uses a catalyst having enhanced catalytic activity and mechanical strength. However, since a dihydric phenolic compound having a high boiling temperature is used as a starting material, the collection of the target product from the reaction mixture needs a large amount of energy, and thus, in industry, a new type of catalyst having a further enhanced catalytic activity is strongly demanded.